The present invention relates to apparatus for separating and partitioning differing-density phases of multiphase fluids, and more particularly to apparatus for separating and partitioning multiphase fluids which utilize gel-like material for partitioning the differing-density phases of such fluids.
The present invention is described in connection with and contemplates an improvement over the multiphase fluid separating and partitioning apparatus shown in U.S. patent application Ser. No. 452,059, now U.S. Pat. No. 3,920,549, filed on Mar. 18, 1974 and assigned to the assignee of the present invention. The apparatus described therein includes a container having an open end and a closed end, gel-like material initially positioned within the container adjacent the closed end, and energizer or flow control means initially partially submerged in the gel-like material for maintaining the gel-like material in its initial position prior to centrifugation and for influencing the gel-like material to flow, under the influence of centrifugal force, along wall portions of the container. The gel-like material is preferably thixotropic and has a density between the densities of the fluid phases to be separated; and the energizer or flow control means employed therein has a density greater than the density of the gel-like material.
The flow control means heretofore used in a blood separation apparatus is shown in FIG. 1. The container 2 is cylindrical in form, having a preferably permanently closed end 3 and an open end 4 provided with a stopper or closure 5. Gel-like material 6 is positioned within the container adjacent one end such as closed end 3. The flow control means 10a, is generally test-tube shaped and includes longitudinally extending equally spaced-apart ribs 11 on its cylindrical sidewall portion. Flow control means 10a is positioned within the gel-like material 6 by suitable means such as directly pushing the flow control means into the gel with a rod or stick. However, this method of seating the flow control means often results in the positioning of sidewall portions of the flow control means substantially adjacent wall portions of the container. That is, as shown in FIG. 1, the flow control means 10a may be positioned off-center or off-axis relative to the longitudinal axis of the container, such that a portion of one of the ribs 11 is separated from the adjacent or proximal portion of the wall of the container 2 only by a thin layer or column of gel-like material 6.
As is further shown by the enlarged sectional view in FIG. 1a, the close positioning of the energizer or flow control member of the conventional type relative to wall portions of the container establishes a capillary column whereby surface tension forces or capillary action cause the gel-like material at the surface level of the column to separate into a grease or thixotropic mixture portion 6 and an oil or liquid portion 6a. The separation of oil portion 6a from thixotropic portion 6 is hereinafter referred to as bleeding. Specifically, when the gel-like material is a thixotropic mixture of silicone oil and an inert siliceous filler, the capillary forces acting on that portion of the gel-like material 6 within the capillary column between the flow control means 10a and container wall 2 sometimes causes a silicone oil portion of the thixotropic gel-like material to bleed from the mixture.
The bleeding of oil or liquid from the gel-like material is a substantial problem because the oil may mix with the fluid to be separated and thus affect the quality of the subsequently separated phases. The oil or liquid used to make the gel-like material employed in a blood separation apparatus normally has a specific gravity lighter than the serum phase of blood; therefore, if the oil bleeds from the gel-like material, it could form a layer or float on top of the serum, or other lighter phase of blood, upon the completion of centrifugation. The layer of oil may also significantly affect the chemistries of the serum which are analyzed under current practice and also may contaminate the associated analytical apparatus, and therefore must be removed before such analysis.
The present invention has overcome the problem of bleeding of the oil or liquid portion from the gel-like material by providing an improved flow control means for use with such gel-like material.